Press with a prestressed frame

ABSTRACT

There is a known prestressed press frame formed by a cylinder cross-member and a counter cross-member of the press and also at least two columns between the cylinder and counter cross-members each column being defined by a stack of sheet metal laminations in tension and a hollow rectangular support member in compression and surrounding the laminations. According to the invention, the perpendicular to the centers of the faces or broad sides of the laminations or plates and to the centers of those walls of the support members which are parallel to the faces or broad sides of the laminations, intersect the press axis.

United States Patent Groos PRESS WITH A PRESTRESSED FRAME 5] Nov. 18, 1975 3,783,774 l/l974 Groos 100/214 Primary E.\'aminerC. W. Lanham Assistant ExaminerRobert M. Rogers Attorney, Agent, or Firm-Holman & Stern ABSTRACT There is a known prestressed press frame formed by a cylinder cross-member and a counter cross-member of the press and also at least two columns between the cylinder and counter cross-members each column being defined by a stack of sheet metal laminations in tension and a hollow rectangular support member in compression and surrounding the laminations. According to the invention, the perpendicular to the centers of the faces or broad sides of the laminations or plates and to the centers of those walls of the support members which are parallel to the faces or broad sides of the laminations, intersect the press axis.

8 Claims, 4 Drawing Figures U.S; Patent Nov. 18, 1975 Sheet10f3 3,919,878

US. Patent Nov. 18, 1975 Shet20f3 3,919,878

U.S.-Patent Nov. 1 8, 1975 sheet of 3,919,878

PRESS WITH A PRESTRESSED FRAME BACKGROUND OF THE INVENTION The invention relates to a press having a prestressed frame of the type comprising two cross-members, usually a cylinder cross-member mounting a cylinder for powering a press ram and a counter cross-member, tie elements in tension interconnecting the cross-members, the tie elements comprising stacks of sheet metal laminations or plates, and hollow rectangular support members in compression and surrounding the stacks of sheet metal laminations. Normal practice is to insert spacer members such as shims or wedges between the ends of the support members and one of the crossmembers to prestress the frame. At least one movable part of the press can be guided by at least one of the support members.

German Offenlegungsschrift No. 1,627,428 discloses a press having a prestressed frame of the type referred to above. There is a stack of sheet metal laminations on each of the four sides of the cross-members.

German Offenlegungsschrift No. 2,048,108 discloses a prestressed press frame in which the tie elements are columns. The support members surround the columns and advantageously have a triangular cross-section, with the triangle apices being directed along the diagonals of the rectangular top cross-member (crown member) and bottom cross-member (press bed). In this case, the support members are additionally provided with cooling ducts.

Both these constructions suffer from the disadvantage that the tie elements must also absorb additional bending stresses which result from elastic deformation of the press cross-members due to press reaction forces taken up by the central zones of the crossmembers, with such bending stresses amounting to approximately 5 to of the tensile stresses. Furthermore, if guideways are welded on the support members for guiding the movable press part, it is no longer certain that the centers of force for the compressive forces in the support members coincide with the respective centers of force for the tensile forces in the tie elements.

SUMMARY OF THE INVENTION The present invention provides a press having a prestressed frame comprising two spaced cross-members, tie elements in tension interconnecting the cross-members, the tie elements comprising stacks of sheet metal laminations or plates, and hollow rectangular support members in compression between the cross-members and surrounding the stacks of metal laminations, the perpendicular to the center of the face of each sheet metal lamination and to the center of those walls of the support members which are parallel to the faces of the laminations intersecting the press axis.

Due to the arrangement of the sheet metal laminations in relation to the press axis, forces are transmitted in a symmetrical arrangement to provide good stress characteristics for the tie elements. As the faces or broad sides of the sheet metal laminations are directed towards the press axis, the bending forces stresses referred to above, which hitherto acted over the entire cross-section of solid tie elements or tie elements of sheet metal laminations in the prior parallel configuration, are ineffective. According to the invention, the bending stresses are, instead, distributed over the individual sheet laminations merely as additional tensile 2 stresses, with the sheet metal laminations or plates closest to the press axis absorbing a higher tensile stress than the sheet metal laminations which are further from the press axis. The inner laminations or plates stretch a bit more than the outer laminations.

The cross-members preferably have rectangular openings which are open to the side (i.e. laterally, to the outside) and accommodate the respective stacks of sheet metal laminations, the perpendicular to that side of each respective opening which is nearest the press axis intersecting the press axis.

Preferably, each support member comprises two generally U-shaped half-shells which are connected to each other. If the sheet metal laminations have hammer head end portions, the half-shells preferably meet along those two sides of the support members which do not lie between the projecting parts of the hammer head end portions.

If the sheet metal laminations have hammer head end portions, two of the side walls of each support member are preferably thicker than the other two, with those two side walls which are thicker lying between the projecting parts of the hammer head end portions. Additional stress deflections are avoided because the maximum cross-section of the force-transmitting parts, i.e. of the support members, is thus disposed directly between the hammer head end portions.

Preferably, at least one, and most preferably at least two, of the support members is provided with a guideway for guiding at least one movable part of the press, the guideway being connected to the respective support member such that the guideway can move axially with respect to the support member, for instance being connected by means of swinging or pivoting ties. Any axial extension or expansion, or compression or contraction, of the support member is thus not transmitted to the guideway. If there are at least two guideways, this can ensure that the guideways, which may be used to guide, for instance, a press ram and a container holder, have guide surfaces in planes intersecting the press axis or the theoretical thermal center of the press, and the conventional base frame, which hitherto supported the guideways, can be omitted. Those planes which extend from the guide surfaces up to the press axis may form an X or an inverted V as seen in cross-section, depending upon whether there are four or two guideways.

BRIEF DESCRIPTION OF THE DRAWINGS One embodiment of the invention is described below, by way of example, with reference to the accompanying drawings, in which:

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT A cylinder cross-member or platen 2 and a counter cross-member or platen 3 of the press are carried on a support frame 1 and form a press frame by means of tie members comprising stacks of separate and unbonded sheet metal laminations or plates 4 as can be seen in FIGS. 2 and 4. The laminations are provided with hammer head end portions 5 and support members in the form of rectangular compression supports 6 which surround the sheet metal laminations 4, with the press being prestressed by means of spacer members in the form of shims or wedges 7 inserted between the ends of the compression support 6 and the respective cylinder platen 2 or counter platen 3.

The sheet metal laminations 4 are disposed in rectangular recesses 8 (see FIG. 2) in the cylinder platen 2 and in the counter platen 3, with the recesses being open laterally and being covered by plates 9. Register pieces 11 (see FIG. 3) are provided between the hammer head end portions 5 of the sheet metal laminations 4 and outer end faces of the cylinder platen 2 and counter platen 3.

Each lamination is of generally rectangular cross-section and has two parallel broad sides or faces and two narrow sides or edges. Each compression support 6 has four walls or sides, two of which are parallel to the faces of the respective laminations. The stacks of sheet metal laminations 4 are arranged symmetrically about the press axis and each individual stack is symmetrical about the radius to the press axis on which it lies, i.e. the perpendicular to the center of the face of each of the sheet metal laminations 4 intersects the press axis. Likewise, the perpendicular to the center of those walls of each compression support 6 which are parallel to the faces of the respective laminations intersects the press axis.

Each compression support 6 comprises two generally U-shaped half-shells which are connected to each other to form a hollow rectangular member; the half-shells meet along those sides of the support 6 which do not lie between the projecting parts of the hammer head end portions 5. The connection is obtained by connecting means in the form of welded plates 12 (see FIG. 4) which join the two half-shells. Those sides 6a of the compression supports 6 which lie between the projecting parts of the hammer head end portions 5 have a greater wall thickness than the other two sides. Guideways 13 on which a movable press part or ram 15 connected to a piston 14 and a container holder 16 are guided are disposed on the upper outwardly facing sides 6a of the compression supports 6. The piston 14 slides in a cylinder 17 (see FIG. 1) mounted by the cylinder platen 2. Pressure medium is supplied to the cylinder 17 via a connection 18. Slide rods 19 (see FIG. 2) for the initial feed and subsequent retraction of a press plunger or extrusion punch 15a are provided on the side of the ram 15 and co-operate with appropriate piston-cylinder units 20 (see FIG. I) mounted on the cylinder platen 2. The press plunger or extrusion punch 15a is mounted on the ram 15 in a conventional manner and extends along the press axis. The container holder 16 is also provided with sliding rods 21 (see FIG. 2) which are connected to appropriate piston-cylinder units 22 mounted on the cylinder platen 2.

The guideways 13 are connected to the sides 6a of the compression supports 6 by pivoting ties 23 (see FIG. 4) which are in tension. The pivoting ties 23 are screwed into cylindrical pivot bosses in cylindrical openings in walls 24 of the compression supports 6 and the bosses 25 can rotate about respective axes, with the axis for the bosses 25 shown in FIG. 4 lying in the plane of the drawing. The appropriate parts of the half-shell (forming part of the compression support 6) are cut away to allow the ties 23 to pivot through a small angle.

The pivoting ties 23 have heads 26 engaging the guide-- ways 13 by way of diaphragm springs 27.

On its side facing the compression support 6, each guideway 13 has a number of axially-spaced longitudinal keyways 28 and keys 29, disposed in the respective sides 6a of the compression supports 6, can slide axially in these key-ways 28.

Any axial deformation of the compression supports 6 is not transmitted to the guideways 13 owing to the type of connection between the guideways l3 and the compression supports 6.

The guideways 13 have replaceable wear strips 13 which are suitably fixed in position.

A die system 30 which is movable perpendicular to the press axis is provided between the container holder 16 and the counter platen 3 of the press. A cropping device 31 is provided on the counter platen for shearing the discard off the extruded strand after an extrusion operation.

If one considers the cylinder platen and counterplaten 3 of the press to have planar faces facing one another when the press is not in operation, the platens 2, 3 are dished very slightly during the extrusion operation because the reaction to the extrusion forces is taken up in the central regions of the platens while the tensile forces are applied at the peripheral regions of the platens. If the tie members were each formed of a single piece of material rigidly connected to the respective platens 2, 3, the very slight dishing of the platens 2, 3 would cause the tie members to bow very slightly towards the press axis due to the application of bending forces at the ends of the tie members. However, such bowing is substantially avoided in the press of the invention.

The very slight dishing of the platens 2, 3 stretches and increases the tension in those laminations 4 which are nearer the press axis and to a certain extent slightly decreases the tension in those laminations 4 which are farther away from the press axis thereby distributing the bending stresses as tensile stresses over the width of each tie member; laminations or plates closest to the press axis absorb a higher tensile stress than the lamina tions which are further from the press axis. However, in each stack, the differences in tension are very much smaller than the pre-stressed tension applied to the whole stack, making each tie member relatively stiff.

I claim:

1. A press comprising a press axis; a cylinder crossmember; press ram means; cylinder means mounted by said cylinder cross-member for moving said press ram means along the press axis; a counter cross-member; at least two tie members in tension interconnecting said cylinder cross-member and said counter cross-member, each said tie member comprising a stack of separate and unbonded sheet metal laminations each said lamination being of generally rectangular cross-section and having two parallel broad sides and two narrow sides, the perpendicular to the center of each said broad side intersecting said press axis so that the laminations closest to the press axis absorb a higher tensile stress than the laminations which are further from the press axis; hollow rectangular support members in compression between said cross-members and surrounding said stacks of sheet metal laminations, said support members comprising four walls, two of which walls are parallel to said broad sides of said laminations, the perpendicular to the center of each of said two walls intersecting said press axis; and spacer members between at least one said cross-member and respective ends of said support members to prestress a press frame formed by said cross-members, said tie members and said support members.

2. The press of claim 1, wherein each of said cylinder cross-member and said counter cross-member defines rectangular openings accommodating said stacks of laminations, said openings being open towards the side of each said cross-member and the perpendicular to that side of each said opening which is nearest said press axis intersecting said press axis.

3. The press of claim 1, wherein each said support member comprises two generally U-shaped half-shells and connecting means connecting said half-shells to each other.

4. The press of claim 3, wherein said laminations have hammer head end portions providing laterallyprojecting parts and wherein said half-shells meet along those two said walls of said support members which do not lie between said projecting parts.

5. The press of claim 4, wherein two parallel said walls of each said support member are thicker than the other two said walls, with said two thicker walls lying 7. The press of claim 1, wherein said press comprises at least two guideways on two respective said support members, pivoting tie means securing said guideways on said support members for axial movement with respect to said support members, and at least one movable press part guided by said guideways.

8. A press comprising a press axis; a cylinder crossmember; press ram means; cylinder means mounted by said cylinder cross-member for moving said press ram means along a press axis; a counter cross-member; at least three tie members in tension interconnecting said cylinder cross-member and said counter cross-member, each said tie member comprising a stack of separate and unbonded sheet metal laminations, each said lamination being of generally rectangular cross-section and having two parallel broad sides and two narrow sides, the perpendicular to the center of each said broad side intersecting said press axis so that the laminations closest to the press axis absorb a higher tensile stress than the laminations which are further from the press axis; hollow rectangular support members in compression between said cross-members and surrounding said stacks of sheet metal laminations, said support members comprising four walls, two of which walls are parallel to said broad sides of said laminations, the perpendicular to the center of each of said two walls intersecting said press .axis; and spacer members between at least one said cross-member and respective ends of said support members to prestress a press frame formed by said cross-members, said tie members and said support members. 

1. A press comprising a press axis; a cylinder cross-member; press ram means; cylinder means mounted by said cylinder crossmember for moving said press ram means along the press axis; a counter cross-member; at least two tie members in tension interconnecting said cylinder cross-member and said counter cross-member, each said tie member comprising a stack of separate and unbonded sheet metal laminations each said lamination being of generally rectangular cross-section and having two parallel broad sides and two narrow sides, the perpendicular to the center of each said broad side intersecting said press axis so that the laminations closest to the press axis absorb a higher tensile stress than the laminations which are further from the press axis; hollow rectangular support members in compression between said cross-members and surrounding said stacks of sheet metal laminations, said support members comprising four walls, two of which walls are parallel to said broad sides of said laminations, the perpendicular to the center of each of said two walls intersecting said press axis; and spacer members between at least one said cross-member and respective ends of said support members to prestress a press frame formed by said cross-members, said tie members and said support members.
 2. The press of claim 1, wherein each of said cylinder cross-member and said counter cross-member defines rectangular openings accommodating said stacks of laminations, said openings being open towards the side of each said cross-member and the perpendicular to that side of each said opening which is nearest said press axis intersecting said press axis.
 3. The press of claim 1, wherein each said support member comprises two generally U-shaped half-shells and connecting means connecting said half-shells to each other.
 4. The press of claim 3, wherein said laminations have hammer head end portions providing laterally-projecting parts and wherein said half-shells meet along those two said walls of said support members which do not lie between said projecting parts.
 5. The press of claim 4, wherein two parallel said walls of each said support member are thicker than the other two said walls, with said two thicker walls lying between said projecting parts.
 6. The press of claim 1, wherein said laminations have hammer head end portions providing laterally-projecting parts, and wherein two parallel said walls of each said support member are thicker than the other two said walls, with said two thicker walls lying between said projecting parts.
 7. The press of claim 1, wherein said press comprises at least two guideways on two respective said support members, pivoting tie means securing said guideways on said support members for axial movement with respect to said support members, and at least one movable press part guided by said guideways.
 8. A press comprising a press axis; a cylinder cross-member; press ram means; cylinder means mounted by said cylinder cross-member for moving said press ram means along a press axis; a counter cross-member; at least three tie members in tension interconnecting said cylinder cross-member and said counter cross-member, each said tie member comprising a stack of separate and unbonded sheet metal laminations, each said lamination being of generally rectangular cross-section and having two parallel broad sides and two narrow sides, the perpendicular to the center of each said broad side intersecting said press axis so that the laminations closest to the press axis absorb a higher tensile stress than the laminations which are further from the press axis; hollow rectangular support members in compression between said cross-members and surrounding said stacks of sheet metal laminations, said support members comprising four walls, two of which walls are parallel to said broad sides of said laminations, the perpendicular to the center of each of said two walls intersecting said press axis; and spacer members between at least one said cross-member and respective ends of said support members to prestress a press frame formed by said cross-members, said tie members and said support members. 